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I'm assembling this addressable RGBW LED strip setup that is 3m long and 60 LEDs/m. I have found no answer to my two questions on other sites or youtube.

(This is the strip I'm using: https://www.adafruit.com/product/2842?length=3) (5VDC, SK6812)

Every LED draws 80 mA on full brightness. Therefore (80*60*3) the maximum draw of the strip would be 14.4A. I'm definitely not gonna use that much as it has dedicated white LEDs, so let's say that I'll be using 10.8A (60*60*3).

1.) If I hooked everything up like this picture shows: enter image description here

Wouldn't the roughly 11A from the power supply fry the arduino? And can the strip's leads really handle 11 amps?

2.) How would you suggest that someone set this up? I want to be able to run both the arduino and the strip off of the same power supply.

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  • \$\begingroup\$ Welcome to EE.SE. Please add the photos / schematics into your post so that readers don't have to follow links to understand your question. \$\endgroup\$ – Transistor Mar 15 at 19:50
  • \$\begingroup\$ 11A is too much for that connector, but your uno is fine as shown... You need to run several power rails to the LEDs, not just at one end, but at least on both ends, and likely several middle points as well. If you don't, the LEDs further away from the power input will sag in voltage and not be as bright or not work at all. \$\endgroup\$ – dandavis Mar 15 at 20:05
  • \$\begingroup\$ Worst case if you flash your 10A load really fast like 20Hz the cap ripple current might be exceeded and go like popcorn with maybe 0.5Arms ripple current \$\endgroup\$ – Sunnyskyguy EE75 Mar 15 at 21:50
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There are a few useful guides on the Adafruit website about powering these strips, including this one showing the addition of power taps.

enter image description here

The flexible pcb won't handle the current of a long chain fed from a single end without excessive drop in voltage to the far end (if not burning out the traces at the start end competely) and causes color changes along the chain, so you need to connect taps in every meter or so with heavier wires in parallel so that each LED is no more than half a meter away from a tap held close to the nominal supply voltage.

If the current draw is too much for a single supply, you can break the 5V supply every so far, and power each section from a different supply . In any case, the only current flowing to the Arduino is its own supply current.

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  • \$\begingroup\$ Distributed AWG20 minimum sharing 10A with 66mohms /m *10A drops 660mV /m or 13% thus when used every meter reduces the voltage drop. Your reference is the best advice +1 \$\endgroup\$ – Sunnyskyguy EE75 Mar 15 at 22:34
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    \$\begingroup\$ This answer is simply NOT true. The NEOPixels are very tolerant to variations in the 5V supply. The onboard controller (WS2811) has a boost converter that converts 5V to 12V and the LED drive is a CC drive. Color and brightness will be consistent with a strip power of 3.3V to 5.3V. You DO NOT need extra wires every meter, but it is a good practice to power the strip from both ends. \$\endgroup\$ – Jack Creasey Mar 16 at 4:03
  • \$\begingroup\$ @JackCreasey - Why then did Adafruit say that? You are saying they won't turn brown due to voltage drop? It seems like an awfully specific thing to be wrong about. \$\endgroup\$ – Bort Mar 16 at 13:39
  • \$\begingroup\$ @Bort I'm sure they do turn brown at some point.....but if you examine the datasheet for the WS2811 you will see that the IC works from 3.3 - 5.3V for the standalone chip.That's an awful lot of voltage range. The version Adafruit seem to have shows a typical variation from 4.5-5.5V (so probably some selected subset of chips): cdn-shop.adafruit.com/datasheets/WS2811.pdf which still allows for at least 500mV of voltage drop along the string. I've used lots of the real chips, and they don't brownout which you'd expect. I do (always) power the string from each end. \$\endgroup\$ – Jack Creasey Mar 16 at 15:02
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Assuming the pin with the 330Ω resistor is data, (be sure to explicitly label all used pins in a diagram in text large enough read), then the current flowing through the LEDs does not flow through the Arduino.

The power to the LEDs will come from your mysterious power supply (not shown or described), at the bottom of your diagram. Out one end, in the other.

The data pin is what controls the LEDs, but is strictly for data. The current seen on that line may very well be less than 1mA, depending on several factors. The control circuitry in the LED strip "reads" the data and then opens/closes the power circuit to the LEDs.

The strips "leads" should be able to handle 10A if they are soldered to, perhaps not if they are simply "clamped". The Adafruit link for that strip says they sell a 10A supply that will power 4 meters of that strip..."Depending on use".

Aside from your question, I would be careful putting more than 10A on a 2.1mm jack. Some "name brands" are rated for about 10, but cheap ones may melt. Be sure to use thick wire too.

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  • \$\begingroup\$ Thanks for your very clear answer. I've seen that link to the 10A supply but I don't understand how that'd be enough. Shouldn't total draw = draw/LED * Number of LED/m * m ? As for the current through the arduino... how does the current not flow through it? \$\endgroup\$ – Krille002 Mar 15 at 20:40
  • \$\begingroup\$ Thanks for the suggestion regarding the 2.1mm jack and my diagram. I'll be sure to solder thick enough wires to the strip instead. And I'll be sure to label my diagrams better in the future. \$\endgroup\$ – Krille002 Mar 15 at 20:45
  • \$\begingroup\$ I think by "Depending on use" they mean "Up to 4 meters if you run them at half power)". \$\endgroup\$ – Bort Mar 15 at 20:52

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